Polyglycol lubricants have been widely and successfully used in a number of different applications for a number of years. They have been used, for example, as special purpose lubricants, hydraulic fluids, brake fluids, metal forming lubricants, automotive engine lubricants and in other applications they are notable for the wide viscosity range in which they are available and for their generally superior viscosity indices; they have also demonstrated particular utility in high temperature applications because of their outstanding response to anti-oxidant additives. When properly inhibited, polyglycol lubricants are relatively stable toward oxidation and pyrolysis at temperatures as high as 200.degree. C. or even higher. Furthermore, the products of oxidative and thermal degradation are either volatile or soluble in the residual lubricant so that problems of sludge deposition are minimized. In addition, the polyglycols show a minimal tendency to the formation of varnish and other highly carbonaceous deposits even when exposed to decomposition temperatures for prolonged periods of time.
Polyglycol derivatives that have been widely used as lubricants are described, for example, in U.S. Pat. Nos. 2,425,755; 2,448,664; 2,520,611 and 2,520612.
However, there is a continuing need to improve the properties of these materials even further so that their potential utility may be further enlarged and their desirable properties exploited to the full. One area where improvements are desirable is in the contribution of the fluid to the formation of an elastohydrodynamic (EHD) film under pressure. This contribution, which is a function of the viscosity and the pressure-viscosity properties of a lubricant, is a measure of how well the lubricant will perform under conditions of extreme pressure. Improvements in this property are therefore desirable in order to improve the high pressure lubricating characteristics of the lubricant.